Electron Arrangement Worksheet | Atomic Model Activity - Free Printable

Let's solve this step by step. The task is to complete the Bohr models (electron arrangements) for each element and fill in the correct number of protons, neutrons, electrons, as well as the atomic number and atomic mass.

We’ll use standard atomic data from the periodic table. Here’s how we determine each value:

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🔹 Key Concepts:

- Atomic Number = Number of protons = Number of electrons (in a neutral atom)
- Atomic Mass ≈ Protons + Neutrons (rounded to nearest whole number)
- Neutrons = Atomic Mass − Atomic Number
- Electrons are placed in shells following the 2, 8, 8... rule (first shell holds 2, second holds 8, etc.)

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Now let's go through each element:

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✔ Hydrogen (H)

- Atomic Number: 1 → Protons = 1, Electrons = 1
- Atomic Mass: ~1.008 → Rounded to 1
- Neutrons: 1 − 1 = 0
- Electron Arrangement: 1 electron in first shell (K-shell)

🔹 Bohr Model: One dot on the innermost circle.

| Protons | 1 |
|--------|---|
| Neutrons | 0 |
| Electrons | 1 |
| Atomic Number | 1 |
| Atomic Mass | 1 |

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✔ Carbon (C)

- Atomic Number: 6 → Protons = 6, Electrons = 6
- Atomic Mass: ~12.01 → Rounded to 12
- Neutrons: 12 − 6 = 6
- Electron Configuration: 2 in first shell, 4 in second shell

🔹 Bohr Model: 2 dots in first shell, 4 dots in second shell.

| Protons | 6 |
|--------|---|
| Neutrons | 6 |
| Electrons | 6 |
| Atomic Number | 6 |
| Atomic Mass | 12 |

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✔ Oxygen (O)

- Atomic Number: 8 → Protons = 8, Electrons = 8
- Atomic Mass: ~16.00 → 16
- Neutrons: 16 − 8 = 8
- Electron Configuration: 2 in first shell, 6 in second shell

🔹 Bohr Model: 2 dots in first shell, 6 dots in second shell.

| Protons | 8 |
|--------|---|
| Neutrons | 8 |
| Electrons | 8 |
| Atomic Number | 8 |
| Atomic Mass | 16 |

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✔ Sulfur (S)

- Atomic Number: 16 → Protons = 16, Electrons = 16
- Atomic Mass: ~32.07 → 32
- Neutrons: 32 − 16 = 16
- Electron Configuration: 2 in first shell, 8 in second, 6 in third

🔹 Bohr Model: 2 in first, 8 in second, 6 in third shell.

| Protons | 16 |
|--------|----|
| Neutrons | 16 |
| Electrons | 16 |
| Atomic Number | 16 |
| Atomic Mass | 32 |

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✔ Nitrogen (N)

- Atomic Number: 7 → Protons = 7, Electrons = 7
- Atomic Mass: ~14.01 → 14
- Neutrons: 14 − 7 = 7
- Electron Configuration: 2 in first shell, 5 in second shell

🔹 Bohr Model: 2 in first, 5 in second shell.

| Protons | 7 |
|--------|---|
| Neutrons | 7 |
| Electrons | 7 |
| Atomic Number | 7 |
| Atomic Mass | 14 |

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✔ Boron (B)

- Atomic Number: 5 → Protons = 5, Electrons = 5
- Atomic Mass: ~10.81 → 11 (rounded)
- Neutrons: 11 − 5 = 6
- Electron Configuration: 2 in first shell, 3 in second shell

🔹 Bohr Model: 2 in first, 3 in second shell.

| Protons | 5 |
|--------|---|
| Neutrons | 6 |
| Electrons | 5 |
| Atomic Number | 5 |
| Atomic Mass | 11 |

> ⚠️ Note: Boron has two isotopes; most common is B-11 (5 protons, 6 neutrons), so atomic mass rounded to 11 is acceptable here.

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✔ Helium (He)

- Atomic Number: 2 → Protons = 2, Electrons = 2
- Atomic Mass: ~4.00 → 4
- Neutrons: 4 − 2 = 2
- Electron Configuration: 2 electrons in first shell (full)

🔹 Bohr Model: 2 dots in first shell.

| Protons | 2 |
|--------|---|
| Neutrons | 2 |
| Electrons | 2 |
| Atomic Number | 2 |
| Atomic Mass | 4 |

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🧪 Final Answer Summary Table:

| Element | Protons | Neutrons | Electrons | Atomic Number | Atomic Mass |
|-------------|---------|----------|-----------|---------------|-------------|
| Hydrogen | 1 | 0 | 1 | 1 | 1 |
| Carbon | 6 | 6 | 6 | 6 | 12 |
| Oxygen | 8 | 8 | 8 | 8 | 16 |
| Sulfur | 16 | 16 | 16 | 16 | 32 |
| Nitrogen | 7 | 7 | 7 | 7 | 14 |
| Boron | 5 | 6 | 5 | 5 | 11 |
| Helium | 2 | 2 | 2 | 2 | 4 |

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🖼️ How to Draw the Bohr Models:

For each element, draw electrons in concentric circles (shells):

- Shell 1 (innermost): Max 2 electrons
- Shell 2: Max 8 electrons
- Shell 3: Max 8 (for these elements)

Example: Oxygen (8 electrons)
→ First shell: 2 electrons
→ Second shell: 6 electrons

Place dots around the circle, evenly spaced.

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✔ Final Step: Fill in the blanks on the worksheet using the values above and draw the electrons accordingly.

Let me know if you'd like a visual sketch or printable version!